NOTHING dates the 1987 movie Wall Street like the $4000 cellphone clutched by financier Gordon Gekko. It was the size of a brick and he could only talk for 30 minutes before having to recharge it.

In the 1980s, it was difficult to imagine the capabilities of today's smartphones. Cellphone users and engineers alike would have considered it unlikely, if not impossible, that so much could be packed into such a small case. To understand why, consider this: if you were to try building an iPhone using equivalent components from the 1980s, just how big would that phone be?